To create the shaman/animist as a class with its own mark or personality is possible, but it would need some time and work, and the feedback
I imagine shaman like a mixture of two previous classes with special game mechanics, the vestige pact binder (3.5 Tome of Magic) and the totemist (Magic of Incarnum). The shaman would summonig a special spirit patron, and this would give a exclusive mini-list of spells, until it was replaced by a new summoning. And the shaman would summon a spirit ally, but the shaman could spend essence points, for a limited time, to unlock special talents of the spirit monter ally, for example effects as metamagic feats, or adding new monster traits, like better natural armor or weapons.
Of course this should be designed for a simple and fast gameplay.
What would be the place for the D&D animist? The summoner. There are players who like to play with monster allies.
* I suggest to add the "Invisible Landscape" as the transitive plane home of the spirits summoned by the shaman/animist.